Transfer circuit



Jan. 17, 1961 J. H. LANE x-:T AL

TRANSFER CIRCUIT Filed Jan, 50, 1958 R. m fm m m AW f VL NM /m .f Y BUnited States Patent "i TRANSFER CIRCUIT John H. Lane, Altadena, andVictor M. Walker, South Pasadena, Calif., assignors to BurroughsCorporation, Detroit, Mich., a corporation of Michigan Filed Jan. 30,1958, Ser. No. 712,182

3 Claims. (Cl. 340-174) This invention relates to magnetic storagedevices and more particularly to a transfer circuit for conveyinginformation from one magnetic element to another.

This invention is an improvement over the application of T. C. Chen andR. A. Tracy entitled Magnetic Device bearing Serial No. 498,257, filedon March 31, 1955, and assigned to the same assignee as thisapplication.

When magnetic elements such as magnetic cores are employed forinformation storage purposes, it is often essential or desirable totransfer information from one magnetic core to another. To accomplishthis, various sorts of transfer circuits have been employed and resortmade to various techniques. Basically there is the problem of reliablytransferring information in the least possible time with a minimum ofdriving power. Normally where more speed is desired, greater power isrequired and this results in overloading the driving equipment with aconsequent impairment of reliability. With these considerations in mindand with due regard for economies in manufacture and repair, a transfercircuit is provided according to the present invention which isrelatively simple in construction, reliable in operation and capable ofperforming at a much greater speed than such previously known devices,

ln a preferred embodiment of this invention, information transferredfrom a rst core to a second core is conveyed by a transfer circuitincluding an output winding on the first core, an input winding on thesecond core, a diode connected between the two windings to prevent theflow of reverse currents and a switch device such as a. transistor,vacuum tube or the like connected between the two windings. The switchdevice normally is biased into a current conductive state, closing thecircuit between the two windings. A second winding is provided on thesecond core and connected to the switch device in a manner to overcomethe effect of the bias and inhibit current conduction during a resetoperation of the second core. As long as inforamtion signals arepresented to the transfer circuit by the first core the switch deviceremains closed, and these signals are conveyed to the second core. Whenthe second core is reset, the second winding thereon causes the switchdevice to be opened and current iow inhibited in the transfer circuitduring the period the second score undergoes a change in magnetic statein a reset operation. In effect the transfer circuit decouples the firstand second cores whenever the second core is reset. This reduces thepower required to reset the second core which thereby relieves the powerrequirements of the driving equipment, resulting in increasedreliability of operation. In addition the period of a reset operation isdecreased thereby permitting the transfer of information from onemagnetic core to another in a shorter period. Hence the speed ofoperation may be increased by approximately a factor of two over somepreviously known devices.

These and other features of this invention may be more Patented Jan. 17,1961.A

fully appreciated when considered in the light of the followingspecification and drawings in which:

Fig. 1 shows one illustrative circuit arrangement incorporating theprinciples of the present invention;

Fig. 2 illustrates the manner in which one ofthe cores in Fig. 1 isoperated along its hysteresis characteristic curve;

Fig. 3 illustrates the manner in which the other core in Fig. 1 isoperated along its hysteresis characteristic curve.

Referring first to Fig. 1, magnetic elements 10 and 12 are coupled by atransfer circuit designated generally at 14. While the type ofinformation transferred between the cores may be any one of severaltypes employed for mathematical or other logical functions, a countingdevice is arbitrarily selected for illustrative purposes. In the usualsequence of operations for a device of this sort, pulses to be countedare applied to a terminal 16 from a pulse source 15 and are temporarilystored in the magnetic element 10, preferably a magnetic quantizingcore, and is subsequently conveyed through the transfer circuit 14 tothe magnetic element 12 which may be a magnetic core also arranged as acounting core. The quantizing core 1) receives the pulses to be countedand provides a quantizing output pulse proportioned to step the countcore 12 up its hysteresis characteristic a preselected amount. Aspointed out subsequently, the magnetic counting core 12 requires ninepulses in order to change it from its initial magnetic state to theopposite magnetic state. Each pulse causes the core to step up itshysteresis curve substantially the same amount to assume a differentcondition of magnetization along its characteristic curve. The tenthpulse causes the magnetic core 12 to be reset to its initial magneticstate, in a manner explained subsequently. It is now apparent thatfunctionally the magnetic core 10 acts as a quantizer core and themagnetic core 12 as a count core.

Pulses applied to an input terminal 16 develop a voltage drop across aresistor 18. The pulses are applied through a winding 20 and an RCnetwork, including a resistor 22 and a condenser 24, to a basevelectrode 26 of a transistor 28. Each pulse applied to the terminal 16is sufficiently negative to overcome the effect of a positive cutoffbias applied through a resistor 30 to the base electrode 26 and causecurrent conduction from the emitter electrode 32 to the collectorelectrode 34. The emitter electrode 32 is connected to ground while thecollector electrode 34 is connected through a winding 36 to a negativesource of voltage. Because of the cutoif bias applied to the baseelectrode 26, no current normally flows through the transistor 28. Whena negative pulse is applied to the input terminal 16, suflicient inmagnitude to overcome the biasing effect of the positive 4 volts,current flows from the emitter 32 to the collector 34 through thewinding 36 to the negative source of voltage. Because of the currentflow through the winding 36, the magnetic core 10 commences to changeits magnetic state, and as a result of this change a signal is inducedin the winding 20 which aids the input signal at the terminal 16 toovercome the cutoff bias applied to the base 26. The input signal has ashort duration but is sufficiently long to insure that the feedbackaction from the winding 36 to the winding 20 is initiated. After theinput signal terminates the positive feedback action between the winding36 and the winding 20 continues to maintain the transistor 28 in theconductive condition until the magnetic core 10 undergoes a completechange in magnetic state.

Referring now to Fig. 2, the changes which take place in the magneticcore 10 are illustrated. Prior to receipt of an input pulse to becounted on the terminal 16 in Fig. 1, the magnetic core 10 is biased ator to the left of the i assegna f point A in Fig. 2by a direct currentowing through a winding 40 in Fig. 1. This current is supplied from anegative source of voltage through a resistor 41, a choke 42 and thecoil 4t) to ground. As soon as an input pulse to the terminal 16V causescurrent conduction in the emitter-collector circuit of the transistor28, the magnetization of the core 10 changes toward the'point B in Fig.2. Once the change in iiux of the core 18 is initiated the feedbackaction between the windings 36 and 20 maintains the transistor 28 in theconductive state, and the magnetization of the core 10 passes throughthe point B in Fig. 2 and continues toward the point C. As themagnetization of the core 1G approaches the point C, the feedbackbetween the winding 36 and the winding 20 commences to decrease. Thiscauses the effective bias at the base electrode 26 to become slightlymore positive. rThe effect is to reduce current conduction in thetransistor 28 which in turn decreases current flow in the winding 36.The feedback to the winding 20 is thus reduced. The decrease in thefeedback signal continues in a cumulative manner until the cutoff biascoupled to the base electrode 26 assumes control and cuts off currentconduction in the transistor 2?. As a result of the D.C. bias in thewinding 48, the magnetization of the core 1d moves from the point C inFig. 2 toward the left to the point-D, then down at or to the'left ofthe point A. A signal is induced in the winding 5d as the core filchanges its magnetization from the point A to the point C in Fig. 2. Asa result of this signal current iiows from the winding 58 to thecollector electrode 52 of a transistor 54, then to the emitter electrode56, through a resistor 58, a winding 60, a diode 62 and back to thewinding Si?. When the core undergoes av change in its magnetic statefrom the point C to the point A in Fig. 2, a signal is induced in thewinding 50, but this signal is of a reverse polarity which isineffective to cause current conduction in the transfer circuit 14because the diode 62 is back-biased and does not conduct.

The quantized signal delivered to the winding 6i) in response to a pulseto be counted causes only an incremental change in the magnetization ofthe core 12. Assuming that the core 12 in Fig. 1 is in the state ofmagnetization indicated by the point E in Fig. 3 when a signal isapplied to the winding 60, the magnetization of the core 12 changes fromthat indicated at point E in Fig. 3 to that indicated at point F. Whenthe signal to the winding 60 terminates the magnetization of the core 12changes from point F- back to the point G. If another pulse is appliedto the input terminal 16 in Fig. 1, the preceding sequence of eventsdescribed with respect to the core 10 and the transfer circuit 14 arerepeated; the winding 60 on the core 12 is pulsed; and the magnetizationof the core 12 moves from point G, out to point F and up to point H.When the pulse signal in the winding 60 terminates, the magnetization ofthe core 12 moves from the point H back along the left to the point I.*In a similar manner subsequent pulses to the input terminal 16 causesthe magnetization of the core 12Ato move upwardly along the line KL inincrements as illustrated. At the end of nine pulses the magnetizationof the core 12 is that indicated by the point M in Fig. 3.

The transistor 54 in Fig. 1 is normally biased in the conductive stateby means of a positive bias sourcecoupled through a resistor- 70 Vto thebase electrode 72.V A positive bias source is connected directly to theemitter electrode 56. A winding 74 and a diode 76 are con,- nec'tedbetween the emitter 56 vand theY base '72." VWhen the transistor 54 isconducting, the voltage drop between the emitter 5 6 and the base 72'ismade less than the breakdown voltage of the diode 76. Consequently nocurrent flows-through the winding 74 and the diode 76, and nomagnetomotive force Vis applied to the c ore 12 by the winding 74. Theplus 4 voltsbias source Acoupled to the emitter 56 is also suppliedthrough the resistor 58, a winding 80, an RC network comprising. aresistor 82 and a condenser 84 to a base electrode 86 of a transistor88. The transistor 88 is normally biased off by means of the positive4-volt bias connected to the resistor 58. Accordingly, the winding 88supplies no magnetomotive force to the magnetic core 12.

The quantized voltage developed across the winding 50 in Fig. l from anyone of the first nine pulses to be counted delivered to the terminal 16is distributed to the various elements serially connected in thetransfer circuit 14. However, the major portion of the signal from thewinding 5t) is developed as a drop across the winding 6G on the magneticcore 12 because the impedance of this winding is very high for each ofthe first nine pulses. The portion of the signal across the winding 50developed as a voltage drop across the resistor 58 is nominal in value,while the voltage drop through the collectoremitter circuit of thetransistor 54 and the voltage drop across the diode 62 are negligiblysmall. When the tenth pulse is applied to the input terminal 16, theresulting pulse across the winding 50 finds a low impedance in thewinding 6l); as a consequence a larger current flows in the transfercircuit 14; and most of the voltage induced in the winding Siisdeveloped as a voltage drop across the resistor 58. It is readily seenfrom Fig. 3 that the tenth pulse finds the magnetic core 12 saturatedand in f the magnetic state indicated by the point M. Since the magneticcore 12 is saturated, little or no back E.M.F. is induced in the winding6d, and hence it has very low impedance. Thus the voltage in the winding50 is developed primarily as a large drop across the resistor S8 and avery small or nominal drop across the winding 60. The voltage drop inthe collector-emitter circuit of the transistor 54 and the drop acrossthe diode 62 remain negligibly small. The relatively large drop acrossthe resistor 58 is of such a polarity as to oppose the plus 4 voltcutoff bias coupled to this resistor. Consequently the voltage dropacross the resistor 58 causes the transistor 88 to become conductive,and current flows from ground to the emitter 94 to a collector electrode92, and through a winding 91) to a negative voltage source. The currentflow in the winding 90 creates a magnetomotive force on the core 12which changes its magnetization from the point M in Fig. 3 toward thepoint R and down along the curve to the point S. In the process a signalis induced in the winding which counteracts the positive 4 volt cutoffbias coupled to the resistor 58, tending normally to bias off thetransistor 88. A positive feedback action is developed between thewindings and 80 on the core 12`which maintains the transistor 88conductive after the termination of the signal induced on the winding 50in substantially the same manner in which the positive feedback actionof the windings 36 and 20 on the core 10 maintained current conductionin the transistor 28 after the termination of an input pulse to theterminal y16. The pulse induced across the windingnS() must terminatebefore the reset action of the core 12 is completed. VHence therelatively large drop developed across the resistor 58 by the tenthpulse serves merely to overcome the positive 4 volt cutoff bias appliedto the base electrode 86 through the resistor 58 and thereby initiatecurrent conduction in the transistor 88. The feedback action between thewindings 90 and 80 maintains the transistor 88 current conductive. Thusconduction of the transistor 88 is insured and current continues to flowthrough the windingr99 while the magnetic core 12 changes its magneticstate from that indicated by point M to that indicated by the point S ofthe curve in Fig. 3V. AsA the magnetization of the core 12 approachesthe point S, the feedback signal from the winding 90 to the winding 80commences to decrease in the manner explained above with respect to thewindings 36 and 20 on the core 10. This decrease in the feedback signalcontinues until the positive 4 volt cutoff bias coupled to the resistor58 assumes control and cuts off current conduction in` the transistor88. When this occurs current ceases to ow in the winding 90, and thestate of magnetization of the core 12 changes from that indicated atpoint S to the condition indicated at point E which is the initial stateof magnetization of the core 12.

It is appropriate at this point to compare the operation of the transfercircuit 14 with and without the transistor 54. Assuming first that thistransistor is omitted and the lower end of the winding 50 and theresistor 58 are directly connected, the transfer circuit 14 is notcapable of being opened during the period when the magnetic core 12 ischanging its magnetic state from that indicated by the point M in Fig. 3to that indicated by the point E, and a large signal is induced in thewinding 60 and applied across the diode 62 in a forward direction.Consequently the transfer circuit 14 tends to conduct a heavy current,and since the energy for this current is supplied ultimately by thenegative voltage source connected to the winding 90, a relatively heavycurrent tiows through the transistor 88. The transistor 88 is operatedin the saturated condition during this period. However, when the core 12reaches the magnetic state indicated by the point S in Fig. 3, little orno signals are induced in the windings 80 and 90. Accordingly, thepositive bias source connected through the resistor 58 to the baseelectrode S6 tends to cut olf current conduction from the emitter 94 tothe collector 92 of the transistor 88. Current conduction in thistransistor does not cease abruptly. Instead, it gradually decays tozero. Since the core 12 undergoes only a slight change in magnetic stateas it changes from the point S in Fig. 3 to the point E, there is littlevoltage induced in the winding 90. Thus the voltage applied between theemitter 94 anud the collector 92 of the transistor 88 is substantiallyequal to the negative voltage source connected to the winding 90, andthe dissipated power in the transistor 88 is extremely high, sometimesas high as one hundred times the average rated power dissipation, duringthis period. Briefly summarizing the foregoing, the transistor SS issaturated and conducts a heavy current when the core 12 changes frompoint M to R to S in Fig. 3. But there is very little voltage dropacross the transistor at this time, and the power dissipation is low. Asthe core 12 changes from point S to E in Fig. 3, current conduction inthe transistor 88 gradually decays to zero. But the voltage from thenegative l volts source connected to the winding 90 is almost entirelyacross the transistor 8S because very little drop is developed acrossthe winding 90 as the core 12 has been switched. Consequently, withcurrent conduction in and relatively high voltage drop across thetransistor 88, the power dissipation is very high, reaching as much asone hundred times the rated power dissipation during the brief periodthe transistor is being turned oil?. This high dissipation tends toshorten the life of the transistor 88, and consequently it is renderedless reliable in operation. In addition, a heavy current in the transfercircuit during a reset operation of the core 12 makes the period of timerelatively long to change the condition of the magnetic core 12 frompoint M in Fig. 3 to point E.

Considering next the operation of the transfer circuit 14 with thetransistor 54 connected therein, assume that the core 12 undergoes achange in magnetic condition from the point M through the points R and Sto the point E in Fig. 3. The transistor 54, the winding 74 and thediode 76 are employed to open the transfer circuit 14. It is recalledthat the diode 76 is normally nonconductive because the drop across theemitter-base circuit of the transistor 54 is less than the forwardthreshold or breakdown voltage of the diode 76. However, a sig-nal isinduced in the winding 74 as the core 12 changes its magnetic conditionduring a reset operation from the point M in Fig. 3 to the point E. Thissignal is sufficient in magnitude and of the proper polarity to causeconduction of the diode 76. Thus the signal induced in the winding 74 isapplied between the base electrode 72 and the emitter 56 of thetransistor 54. It is sutiiciently negative to terminate currentconduction in this transistor. The transistor 54 acts as a switch whichis normally closed but is opened when .a signal is induced in thewinding 74 as the magnetic core 12 changes from the magnetic conditionindicated at point M in Fig. 3 through the points R and S to the pointE. Since the transfer circuit 14 conducts no current during this changein state of the magnetic core 12, considerably less current iiowsthrough the winding and the transistor 88 than in the previouslydescribed instance. Like the above described operation, the positivebias connected through the resistor 58 to the base electrode 86gradually assumes control and terminates current conduction from theemitter 94 to the collector 92 of the transistor 88, and during theprocess the negative voltage source connected to the winding 90 isapplied almost entirely across the transistor 88. However, because themaximum current flow through this transistor is much less in thisinstance, the dissipated power in the transistor 88 is reduced considerably to a value within safe limits. Hence the reliability of thetransistor 88 is increased because its useful life is extended. Also,the time required to reset the core 12 may be substantially decreased,and this may serve to shorten the basic time cycle required to count thecore 12 through a complete cycle of 10 pulses one of which causes areset operation. Accordingly, the repetition rate of pulse applied tothe input termin-al 16 may be increased.

What is claimed is:

1. In combination, a rst magnetic core having an input winding and anoutput winding coupled to the core, said input winding including a pairof windings coupled to said core in a positive feedback arrangement andserially connected by means of a switching element, a source of pulsescoupled to the input Winding whereby the pulses switch the magneticstate of said core, a sec ond magnetic core having an input winding anda reset winding, said reset winding including a pair of windings coupledto the second core in a positive feedback arrangement and seriallyconnected by means of a switching element, a unilateral transfer loopcoupled between the output winding of the first magnetic core and theinput winding of the second core arranged to deliver only pulses of apreselected polarity to the second core, the output winding of the iirstcore is defined to provide pulses for changing the magnetic condition ofthe second core along its hysteresis characteristic from one magneticremanent point to the other remanent point, and circuit means includinga switching winding coupled to the second core switchable between twoconductive conditions and coupled to the transfer loop to control theconductivity thereof and arranged in one conductive condition to deliverpulses from the first core to the second core, said switching winding isarranged to be responsive to the switching of the second core from saidother remanent point to said one remanent point for changing itsconductive condition during this switching interval whereby the feedbackarrangement of said reset winding maintains this changed conductiveconditon for a preselected interval after the termination of the pulseeffective to switch the second core from lthe said other remanent pointto said one remanent point.

2. In combination, a rst magnetic core having an input winding and anoutput winding coupled to the core, a source of pulses coupled to theinput winding whereby the pulses switch the magnetic state of said core,a second magnetic core having an input winding and a reset winding, saidreset winding including a pair of windings coupled to the second core ina positive feedback arrangement and serially connected by means of aswitching element, va unilateral transfer loop coupled between theoutput winding of the first magnetic core and the input winding of thesecond core arranged to deliver only pulses Iof a preselected polarityto the second core, the output winding of the first core is dened toprovide pulses for changing the magnetic conditionn of the second correalong'it's hysteresis characteristic'from one magnetic reinanent pointto the other remanent point, and circuit means switchable between twoconductive conditions and coupled to the transfer loop to control theconductivity thereof and arranged in one conductive condition to deliverpulses from the first core to the second core, said circuit meanscomprising a normally conductive switching element serially connectedwith an impedance device and a 4switching winding coupled to the secondcore, said reset winding is coupled to said circuit means intermediatethe impedance device and the input winding o f said second core tocontrol the switching element for said reset winding and thereby theswitching of the second core from said other remanent point to said oneremanent point, said switching winding is arranged to be re*- sponsiveto the latter mentioned switching of the second core for` changing theconductive condition of the switching element for the circuit meansduring this switching interval whereby the feedback arrangement'of said'reset winding maintains this changed conductive condition fora'presele'cted interval after the termination of Athe pulse from thefirst core effective to switch the second core from the said otherremanent point to said one remanent point.

3. A counter comprising a quantizing magnetic core having at least aninput winding andan outputiwinding coupled to the core, a source ofpulses to be counted coupled to the input winding, a counting magneticcore having at least an input Winding and ay reset winding, each of saidmagnetic cores having a substantially rectangular hysteresis loop, aunilateral transfer loop'c-oupledbe,

tweenthe outputwinding of the quantizing magnetic core and'theinputwinding of the count core arranged to deliver only quantized pulses tobe counted to the count core, the output winding of the quantizing coreas deiined to provide pulses to be counted for stepping the count corealong its hysteresis characteristic from one magnetic remanent point tothe other remanent point in preselected increments, and a circuit meansconnected to the transfer loop for controlling the conductive conditionthereof and arranged in one conductive condition to deliver thequantirzed pulses to be counted to the count core, said circuit meansincluding a switching winding coupled to said count core and arranged tobe responsive to the switching of the count core from said otherremanent point to said one remanent point for changing the oneconductive condition of said circuit means to its other conductivecondition during this'latter mentioned switching interval, said circuitmeans further including impedance means connected to the reset windingfor the count core and providing a signal to said reset winding when thecount core is at the other remanent point effective to switch the countcore to said one remanent point.

References Cited in the tile of this patent UNITED STATES PATENTS2,708,722 An wang May 17, 1955 2,747,110 Jones May 22, 1956 2,772,357 AnWang Nov. 27, 1956 2,808,578 Goodell etal. Oct. 1, 1957 2,825,890 nicherer a1. Mar. 4. 1958 FOREIGN PATENTS 730,165 Great Britain May 18, 1955

